Ankle sprain

I’m sure that we have all sprained an ankle at some point. This is, after all, one of the most common sports injuries there is, with 23,000 to 27,000 ankle sprains apparently being reported daily in the United States alone.

Researchers have tried to find both clinical and laboratory measures that could detect and explain deficits in people with functional ankle instability (FAI). The main drawback with some of the more clinically based assessments is that they are exactly that: clinical. By attempting to control all possible variables, researchers end up using assessments that bear little relation to what actually takes place in sport, and therefore are of limited value in the real world. A dynamic measure is more challenging and potentially more effective for detecting deficits in people with joint instability.

Recently, researchers in Florida picked up on this need to come up with more suitable protocols (‘Detection of Dynamic Stability Deficits in Subjects with Functional Ankle Instability’, Medicine and Science in Sports and Exercise 2005: 37 (2), 169- 175). They tested two protocols to determine which was the more effective for flagging up stability issues:

Step down: step from a 20cm-high platform on to a force plate, leading with the test leg, stabilise as quickly as possible, place hands on hips and look straight ahead for 20 seconds.

Jump: make a two-legged jump to touch an overhead marker (equivalent of 50% max vertical jump height) and land on the test leg, stabilise as quickly as possible, place hands on hips and look straight ahead for 20 seconds.

Both protocols used an objective measure of time-tostabilisation (TTS) as an indication of dynamic stability. The subjects were placed into two groups, healthy and those with FAI. Subjects in the FAI group had sensations of weakness, looseness and episodes of ankles giving way during daily activity, without any history of fracture or injury within the past three months, and no formal rehabilitation of the affected ankle.

The data showed that, when comparing FAI with healthy ankles, the jump protocol was more successful at detecting differences in dynamic stability than the step-down protocol. What makes this test superior?

* The jump protocol creates higher ground reaction forces, which more closely mimic those seen during sporting activities.

* The task is complex, requiring greater eccentric strength, coordination and stability.

* The complexity of the task is thought to ‘switch the lights on’ – initiation of an early co-contraction around the ankle joint before landing to increase muscle stiffness, allowing faster reactions to the landing surface. If you have stability issues you are going to have trouble ‘flicking the switch’.

This research has given health professionals a useful assessment for detecting stability problems in the ankle. While it’s good to see a test that tries hard to get close to athletic movements, both protocols have their own problems. The use of a force platform to detect TTS is probably the biggest and certainly the most obvious!

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Risk factors

Researchers from Sydney Australia have reviewed 21 research articles in an attempt to identify possible risk factors associated with ankle injuries (‘Do Voluntary Strength, Proprioception, Range of Motion, or Postural Sway Predict Occurrence of Lateral Ankle Sprain?’ British Journal of Sports Medicine 2006: 40, 824-828). Several risk factors have been identified as having the potential to increase the chance of a future ankle sprain:

* postural sway

* range of motion

* muscle strength

* proprioception

* previous sprains.

The research team found that the most important predictor of risk of ankle injury was reduced ankle dorsiflexion range of motion. If you have inflexible ankles (the researchers found subjects with as little as 34 degrees dorsiflexion range of movement compared to the average of 45 degrees) then you are nearly five times more likely to sprain your ankle than people with average dorsiflexion flexibility. Postural sway was the next best predictor, followed by proprioception (although the jury still seems to be out on the latter, and it may not be as important as once thought). As for strength, it would appear from the findings of this study that strength is still a bit of an unknown quantity.

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Can stretching help?

Researchers from the University of Western Sydney wanted to find out if static calf muscle stretching had a positive impact on ankle joint dorsiflexion range of movement (‘Does Stretching Increase Ankle Dorsiflexion Range of Motion?’ A Systematic Review, British Journal of Sports Medicine, 40 2006, 870- 875). Five studies were reviewed in which ankle dorsiflexion was measured both actively and passively, weight bearing and non-weight bearing and with the knee extended and flexed. Stretches were performed for anything from 20 secs to 10 mins, depending on the study. In all but one trial, dorsiflexion was measured immediately after stretching.

Calf-muscle tightness and reduced range of ankle joint dorsiflexion are associated with a number of lower limb disorders, such as plantar fasciitis and Achilles tendinitis. Calf-muscle stretches are often prescribed to increase ankle dorsiflexion and reduce the symptoms of such disorders. The review found that calf muscle stretches did, in fact, provide a small but statistically significant increase in ankle dorsiflexion, particularly after 5 to 30 minutes of stretching. So if you want to help reduce your clients’ injury potential, make sure they include ankle flexibility work within their training schedule.

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